EP 0385500 A3 19911211 - OPTICAL HEAD
Title (en)
OPTICAL HEAD
Publication
Application
Priority
JP 4994189 A 19890303
Abstract (en)
[origin: EP0385500A2] An optical head in which reflected laser light is split into two optical paths by a polarized light beam splitter (23) while astigmatisms are produced in the laser light by at least one astigmatism generating element (22), and the two split beams are led so as to be incident upon two quadrant photodetectors, respectively. A focus error signal is obtained as an electrical signal by subtracting the sum of the quantities of light received by one of the diagonal pairs of regions among the quadrant regions of the two photodetectors (24, 25) from the sum of the quantities of light received by the other diagonal pair. This arrangement enables cancelling of influence of double refraction in a magneto-optic disk or the like, thereby making the optical head free of the problem of such influence.
IPC 1-7
IPC 8 full level
G11B 11/10 (2006.01); G11B 7/09 (2006.01); G11B 7/095 (2006.01); G11B 7/13 (2012.01); G11B 7/135 (2006.01); G11B 7/1365 (2012.01); G11B 7/1378 (2012.01); G11B 7/1381 (2012.01); G11B 11/105 (2006.01)
CPC (source: EP US)
G11B 7/0909 (2013.01 - EP US); G11B 7/13 (2013.01 - EP US); G11B 7/1365 (2013.01 - EP US); G11B 7/1378 (2013.01 - EP US); G11B 7/1381 (2013.01 - EP US); G11B 11/10543 (2013.01 - EP US)
Citation (search report)
- [X] EP 0218250 B1 19921230
- [A] EP 0301643 A2 19890201 - LASER MAGNETIC STORAGE INT [US]
Designated contracting state (EPC)
DE FR GB
DOCDB simple family (publication)
EP 0385500 A2 19900905; EP 0385500 A3 19911211; EP 0385500 B1 19950920; DE 69022447 D1 19951026; DE 69022447 T2 19960208; JP 2657413 B2 19970924; JP H02230517 A 19900912; US 5084850 A 19920128
DOCDB simple family (application)
EP 90104111 A 19900302; DE 69022447 T 19900302; JP 4994189 A 19890303; US 48707790 A 19900301